1. Field of the Invention
The present invention relates to a mobile electronic appliance, particularly, to a mobile electronic appliance exhibiting improved impact resistance characteristics.
2. Description of the Related Art
In recent years, a precision unit such as a hard disk, a magnetic disk drive-or an optical drive is housed as a peripheral unit in a mobile electronic appliance such as a notebook type personal computer or a PDA (personal digital assistant). Also, the mobile electronic appliance is generally equipped with a display section and a keyboard section as an interface with the user. Where the mobile electronic appliance of the particular construction is accidentally dropped onto, for example, the ground, the casing of the mobile electronic appliance is possibly broken by the impact, leading to the breakage of the display section or the keyboard section. It is also possible for the precision unit housed in the casing to be broken by the impact.
Structural measures are taken in the conventional mobile electronic appliance of the particular construction in order to prevent the casing and the parts housed in the casing from being broken if the mobile electronic appliance is dropped onto, for example, the ground. For example, it is disclosed in Japanese Patent Disclosure (Kokai) No. 10-322039 and Japanese Patent No. 2392265 that a plurality of small impact resistant members made of, for example, a rubber-series resin are housed as separate members within the casing of the electronic appliance. The impact resistant member is formed of a rubber-series resin such as a urethane-series resin or a silicone-series resin and is mounted in a replaceable manner to the four corners of the casing or around the casing. Alternatively, the particular impact resistant member is fixed to the casing by using, for example, an adhesive. An additional measure for protecting the precision unit housed in the mobile electronic appliance is disclosed in, for example, “IBM Home Page ‘HDD Shock Absorber’, searched for on Jan. 27, 2003, internet <www-6.ibm.com./jp/pc/design/hddshock.html>”. To be more specific, disclosed in this article is an electronic appliance in which a small projection or a buffer member formed integral with the casing is arranged in that region of the bottom portion of the casing which is positioned right under the precision unit housed in the casing. Also disclosed in this article is an apparatus in which that region of the casing which is positioned right under the precision unit is swollen to form a dome configuration so as to produce a buffering effect.
However, in the conventional measure for protecting the electronic appliance by using an impact resistant member as pointed out above, it is necessary to prepare separately the impact resistant member. This gives rise to the problems that the number of parts used is increased and that the material cost and the manufacturing cost are increased. What should also be noted is that used is a rubber-series resin. Since it is difficult to utilize a rubber series resin in a coating operation, the use of the rubber-series resin gives rise to an additional problem that the degree of freedom is impaired in terms of the design. In addition, the mounting strength between the casing of the electronic appliance and the impact resistant member tends to be rendered insufficient so as to give rise to the problem that, when an impact has been applied, the impact resistant member is detached so as to make it difficult to continuously protect the electronic appliance.
Still further, in the protection structure of the electronic appliance, which uses a relatively small projection or buffer member housed in the casing, it is necessary to pay attention to the fact that, if the dropping height is increased, this increase the impact force received from the floor surface. In this case, the bottom portion of the casing tends to be deformed in a local region around the projection or the buffer member. Also, the casing tends to be warped about the fulcrum provided by the projection or the arranging point of the buffer member so as to enlarge the contact region between the casing and the floor surface. Where that region of the precision unit housed in the casing which is positioned right above the contact region is brought into contact with the inner surface of the casing of the electronic appliance under the situation described above, a problem is generated in that a serious impact is imparted to the precision unit housed in the casing. The impact force applied to the precision unit noted above is equal to that in the case where the electronic appliance is dropped directly onto the floor surface. Alternatively, where a turning moment is generated because of the defect in the arrangement of the projection, the impact force noted above is larger than that in the case where the electronic appliance is dropped directly onto the floor surface. Further, where the buffer member or the buffering structure is formed right below the precision unit housed in the casing, an additional problem is generated in that the impact is transmitted directly to the housed precision unit positioned right above the buffer member or the buffering structure in the case where the dropping height is increased so as to lose the buffering effect.